Marcin Kaczmarek (born 25 June 1977 in Pisz, Warmińsko-Mazurskie) is a retired butterfly swimmer from Poland, who competed for his native country at the 2000 Summer Olympics in Sydney, Australia. A member of AZS-AWF Gdańsk he is best known for winning the bronze medal at the 1997 European Swimming Championships in the men's 4×100 m medley relay, alongside Mariusz Siembida, Marek Krawczyk and Bartosz Kizierowski.